Apigenin is one of the flavonoids - more precisely one of the citrus bioflavonoids. Apigenin, just like most flavonoids, has antioxidant, anti-inflammatory, and anti-tumor properties... perhaps apigenin can even block the formation of uric acid leading to beneficial effects in gout.

Apigenin is found in high amounts in parsley, thyme, and peppermint. Apigenin is also found in a number of herbs, including chamomile herb, lemon balm herb, perilla, vervain herb, and yarrow.

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Twice a month we email you a brief abstract of several new studies on various supplements and natural medicine topics and their practical interpretation by Ray Sahelian, M.D. We will mention research updates on apigenin as we come across them.

 

Benefits of apigenin
As with many flavonoids, apigenin has potential to reduce the risk of cancer since it has anti-tumor activity. Apigenin also could potentially be useful in allergic conditions since it can have anti-inflammatory properties.

Apigenin Research Update
Synergistic interaction between hesperidin, a natural flavonoid, and diazepam.
Eur J Pharmacol. 2005 Apr 11;512(2-3):189-98.
It has been recently reported the presence in Valeriana of the flavone 6-methylapigenin and the flavanone glycoside hesperidin. The apigenin derivative is a ligand for the benzodiazepine binding site in the gamma-aminobutyric acid receptor type A (GABA(A)) and has anxiolytic properties. Hesperidin has sedative and sleep-enhancing properties but is not a ligand for the benzodiazepine binding site. 6-Methylapigenin is able to potentiate the sleep-enhancing effect of hesperidin. In this work we demonstrate that this property is shared with various GABA(A) receptor ligands, among them the agonist diazepam, which was used to study the potentiation as measured in the hole board test. Isobolar analysis of the results showed the interaction being synergistic. We discarded pharmacokinetic effects or a direct action of hesperidin on the benzodiazepine binding site. A possible use of hesperidin properties to decrease the effective therapeutic doses of benzodiazepines is suggested.

Dietary flavonoids as proteasome inhibitors and apoptosis inducers in human leukemia cells.
Biochem Pharmacol. 2005 May 15;69(10):1421-32.
Chen D, Daniel KG, Chen MS, Kuhn DJ, Landis-Piwowar KR, Dou QP.
The Prevention Program, Barbara Ann Karmanos Cancer Institute, and Department of Pathology, School of Medicine, Wayne State University, 640 HWCRC, 4100 John R, Detroit, MI
It has been shown that proteasome activity is required for cancer cell survival and consumption of fruits and vegetables is associated with decreased cancer risk. Previously, we reported that grape extract could inhibit proteasome activity and induce apoptosis in tumor cells. In this study, we examined the flavonoids apigenin, quercetin, kaempferol and myricetin for their proteasome-inhibitory and apoptosis-inducing abilities in human tumor cells. Our results suggested that the proteasome may be a target of these dietary flavonoids in human tumor cells and that inhibition of the proteasome by flavonoids may be one of the mechanisms responsible for their cancer-preventive effects.

Apigenin inhibits VEGF and HIF-1 expression via PI3K/AKT/p70S6K1 and HDM2/p53 pathways.
FASEB J. 2005 Mar;19(3):342-53. Fang J, Xia C, Cao Z, Zheng JZ, Reed E, Jiang BH.
The Mary Babb Randolph Cancer Center, Department of Microbiology, Immunology and Cell Biology, West Virginia University, Morgantown, West Virginia
Apigenin is a nontoxic dietary flavonoid that has been shown to possess anti-tumor properties and therefore poses special interest for the development of a novel chemopreventive and/or chemotherapeutic agent for cancer. Ovarian cancer is one of the most common causes of cancer death among women. Here we demonstrate that apigenin inhibits expression of vascular endothelial growth factor (VEGF) in human ovarian cancer cells. VEGF plays an important role in tumor angiogenesis and growth. We found that apigenin inhibited VEGF expression at the transcriptional level through expression of hypoxia-inducible factor 1alpha (HIF-1alpha). Apigenin inhibited expression of HIF-1alpha and VEGF via the PI3K/AKT/p70S6K1 and HDM2/p53 pathways. Apigenin inhibited tube formation in vitro by endothelial cells. These findings reveal a novel role of apigenin in inhibiting HIF-1 and VEGF expression that is important for tumor angiogenesis and growth, identifying new signaling molecules that mediate this regulation.

Ibuprofen and apigenin induce apoptosis and cell cycle arrest in activated microglia.
Neurosci Lett. 2005 Feb 28;375(2):91-6.
In case of injury or disease, microglia are recruited to the site of the pathology and become activated as evidenced by morphological changes and expression of pro-inflammatory cytokines. Evidence suggests that microglia proliferate by cell division to create gliosis at the site of pathological conditions such as the amyloid plaques in Alzheimer's disease and the substantia nigra of Parkinson's disease patients. The hyperactivation of microglia contributes to neurotoxicity. In the present study we tested the hypothesis that anti-inflammatory compounds modulate the progression of cell cycle and induce apoptosis of the activated cells. We investigated the effects of ibuprofen (non-steroidal anti-inflammatory drug) and apigenin (a flavonoid with anti-inflammatory and anti-proliferative properties) on the cell cycle of the murine microglial cell line BV-2. The findings indicate that apigenin-induced cell cycle arrest preferentially in the G2/M phase and ibuprofen caused S phase arrest. The binding of annexin V-FITC to the membranes of cells which indicates the apoptotic process were examined, whereas the DNA was stained with propidium iodide. Both apigenin and ibuprofen induced apoptosis significantly in early and late stages. The induction of apoptosis by ibuprofen and apigenin was confirmed using TUNEL assay, revealing that 25 microM apigenin and 250 microM ibuprofen significantly increased apoptosis in BV-2 cells. The results from the present study suggest that anti-inflammatory compounds might inhibit microglial proliferation by modulating the cell cycle progression and apoptosis.

Flavonoid apigenin inhibits motility and invasiveness of carcinoma cells in vitro.
Int J Cancer. 2005 Mar 10;114(1):12-8.
Investigations of the mechanisms of the cancer-preventive activity of apigenin (4',5,7,-trihydroxyflavone), a plant-derived, anti-carcinogenic flavonoid, showed its interference with cell proliferation, survival, and gap junctional coupling. We used a model based on non-invasive HeLa wild-type cells and their connexin43 (Cx43) transfected counterparts to correlate the effect of apigenin on tumour cell invasiveness with its influence on cell motility. Both cell lines displayed similar motile properties in control conditions. Apigenin treatment resulted in a significant and reversible inhibition of translocation of both HeLa wild-type cells and HeLa Cx43 transfectants. The effect of apigenin on cell proliferation was less pronounced especially at low apigenin concentration, whereas its influence on cell motility correlated with the reduction of the invasive potential of HeLa Cx43 cells as shown by an invasion assay based on the confrontation of tumour cell spheroids with chick embryo heart fragments. HeLa Cx43 cells were highly invasive in controls, but did not invade the heart tissue at tumour cell aggregate-fibroblast capsule interfaces in the presence of apigenin and failed to fully engulf these heart fragments. Because the motility of chick heart fibroblasts was only slightly affected by apigenin, these observations indicate that apigenin exerts its anti-invasive effect on HeLa cells predominantly via a specific inhibition of tumour cell motility. This inhibitory effect of apigenin on tumour cell invasiveness in vitro demonstrates that apigenin may exert its anti-tumorigenic effect in vivo via inhibition of tumour cell penetration of the healthy tissue.

Apigenin induced apoptosis through p53-dependent pathway in human cervical cancer cells.
Life Sci. 2005 Feb 4;76(12):1367-79.
Apigenin is a widely distributed plant flavonoid and was proposed as an antitumor agent. In this study, we reported for the first time that apigenin inhibited the growth of human cervical carcinoma cells (HeLa) and through apoptotic pathway. The results showed that apigenin significantly decreased the viability of HeLa cells at 37-74 microM and the IC50 value was 35.89 microM. Apigenin-induced apoptosis in HeLa cells was confirmed by DNA fragmentation assay and induction of sub-G1 phase by flow cytometry. Apigenin-treated HeLa cells were arrested at G1 phase, which was associated with a marked increment of the expression of p21/WAF1 protein. The induction of p21/WAF1 appeared to be transcriptionally upregulated and was p53-dependent. In addition, apigenin induced Fas/APO-1 and caspase-3 expression which were also correlated with apoptosis. Apigenin decreased in the protein expression of Bcl-2 protein, which is an anti-apoptotic factor. The conclusion of this study is the apigenin induced p53 expression which caused cell cycle arrest and apoptosis. These findings suggest that apigenin has strong potential for development as an agent for preventing cervical cancer.

Decreased pro-inflammatory cytokine production by LPS-stimulated PBMC upon in vitro incubation with the flavonoids apigenin, luteolin or chrysin, due to selective elimination of monocytes / macrophages.
Biochem Pharmacol. 2005 Jan 15;69(2):241-8.
Apigenin and its structural analogues chrysin and luteolin were used to evaluate their capacity to inhibit the production of pro-inflammatory cytokines by lipopolysaccharide (LPS)-stimulated human peripheral blood mononuclear cells (PBMC). Furthermore, flowcytometric analysis was performed to compare the effects of apigenin, chrysin, luteolin, quercetin and naringenin on the different cell types present in PBMC. LPS-stimulated PBMC were cultured in the presence of the flavonoids and TNFalpha, IL-1beta and IL-6 were measured in the supernatants. In parallel, metabolic activity of the PBMC was determined by measuring succinate dehydrogenase activity. Apigenin, chrysin and luteolin dose-dependently inhibited both pro-inflammatory cytokine production and metabolic activity of LPS-stimulated PBMC. With increasing concentration of apigenin, chrysin or luteolin the monocytes/macrophages disappeared as measured by flowcytometry. This also appeared to occur in the non-LPS-stimulated PBMC. At the same time there was an increase in dead cells. T- and B-lymphocytes were not affected. Quercetin and naringenin had virtually no effects on cytokines, metabolic activity or on the number of cells in the studied cell populations. In conclusion, monocytes were specifically eliminated in PBMC by apigenin, chrysin or luteolin treatment in vitro at low concentrations (around 8 microM), in which apigenin appeared to be the most potent.

The flavones luteolin and apigenin inhibit in vitro antigen-specific proliferation and interferon-gamma production by murine and human autoimmune T cells.
Biochem Pharmacol. 2004 Aug 15;68(4):621-9.
Plant-derived flavonoids are inhibitors of various intracellular processes, notably phosphorylation pathways, and potential inhibitors of cellular autoimmunity. In this study, the inhibiting effects of various flavonoids on antigen-specific proliferation and interferon-gamma (IFN-gamma) production by human and murine autoreactive T cells were evaluated in vitro. T-cell responses were evaluated for the human autoantigen alpha B-crystallin, a candidate autoantigen in multiple sclerosis, and for the murine encephalitogen proteolipid protein peptide PLP (139-151). The flavones apigenin and luteolin were found to be strong inhibitors of both murine and human T-cell responses while fisitin, quercitin, morin and hesperitin, members of the subclasses of flavonoles and flavanones, were ineffective. Antigen-specific IFN-gamma production was reduced more effectively by flavones than T-cell proliferation, suggesting that the intracellular pathway for IFN-gamma production in T cells is particularly sensitive to flavone inhibition. These results indicate that flavones but not flavanoles or flavanones are effective inhibitors of the potentially pathogenic function of autoreactive T cells. The effects of flavones were the same for human and murine autoreactive T cells, stressing the usefulness of animal models of autoimmunity for further studies on the effects of flavonones on autoimmune diseases.

Flavonoids such as luteolin, fisetin and apigenin are inhibitors of interleukin-4 and interleukin-13 production by activated human basophils.
Int Arch Allergy Immunol. 2004 Jun;134(2):135-40.
BACKGROUND: We have previously shown that fisetin, a flavonol, inhibits IL-4 and IL-13 synthesis by allergen- or anti-IgE-antibody-stimulated basophils. This time, we investigated the inhibition of IL-4 and IL-13 production by basophils by other flavonoids and attempted to determine the fundamental structure of flavonoids related to inhibition. We additionally investigated whether flavonoids suppress leukotriene C4 synthesis by basophils and IL-4 synthesis by T cells in response to anti-CD3 antibody. Highly purified peripheral basophils were stimulated for 12 h with anti-IgE antibody alone or anti-IgE antibody plus IL-3 in the presence of various concentrations of 18 different kinds of flavones and flavonols. IL-4 and IL-13 concentrations in the supernatants were then measured. Leukotriene C4 synthesis was also measured after basophils were stimulated for 1 h in the presence of flavonoids. Regarding the inhibitory activity of flavonoids on IL-4 synthesis by T cells, peripheral blood mononuclear cells were cultured with flavonoids in anti-CD3-antibody-bound plates for 2 days. Luteolin, fisetin and apigenin were found to be the strongest inhibitors of both IL-4 and IL-13 production by basophils but did not affect leukotriene C4 synthesis. At higher concentrations, these flavonoids suppressed IL-4 production by T cells. Based on a hierarchy of inhibitory activity, the basic structure for IL-4 inhibition by basophils was determined. Due to the inhibitory activity of flavonoids on IL-4 and IL-13 synthesis, it can be expected that the intake of flavonoids, depending on the quantity and quality, may ameliorate allergic symptoms or prevent the onset of allergic diseases.

Antidepressant-like effects of apigenin and 2,4,5-trimethoxycinnamic acid from Perilla frutescens plant in the forced swimming test.
Biol Pharm Bull. 2003 Apr;26(4):474-80.
We studied the effects of apigenin and 2,4,5-trimethoxycinnamic acid (TMCA) on the behavioral despair test (forced swimming test), and the central noradrenergic, dopaminergic and serotonergic activities in mice. Apigenin at intraperitoneal doses of 12.5 and 25 mg/kg significantly decreased the duration of immobility in the forced swimming test in mice. At 100 mg/kg, the duration of immobility was returned to the control level in the test. These behavioral and biochemical results indicate the antidepressant properties of apigenin, which may be mediated by the dopaminergic mechanisms in the mouse brain.

Molecular modeling of flavonoids that inhibits xanthine oxidase.
Biochem Biophys Res Commun. 2002 May 31;294(1):167-72.
The inhibition of xanthine oxidase activity by various flavonoids was assessed. All of the tested flavonoids were competitive inhibitors, and from the kinetic analysis suggested that flavonoids bind to the reactive site. To further understand the stereochemistry between these flavonoids and xanthine oxidase, structure-based molecular modeling was performed. Apigenin was the most potent inhibitor which showed the most favorable interaction in the reactive site. The bicyclic benzopyranone ring of apigenin stacked with phenyl of Phe 914, and the phenolic group stretched to the space surrounding with several hydrophobic residues. Quercetin and myricetin composed a 3-hydroxyl group on benzopyranone which resulting in reduction of binding affinity. The phenolic group of genistein positioned in opposite orientation comparison with apigenin, and resulted in a weaker interaction with xanthine oxidase. Isovitexin showed the weakest inhibitory effect among the compounds tested. The bulky group of sugar in isovitexin may hamper its interaction with xanthine oxidase.

Apigenin questions
Q. Does apigenin have antidepressant properties?
   A. I have not seen studies with apigenin and depression, so I don't know.

Q. Can a flavonoid supplement such as apigenin be used with tongkat ali LJ100?
   A. Probably, but keep dosages low.

Q. Excellent review of the pathways associated with apigenin, Luteolin- flavones etc. Briefly, I find Apigenin in combination with the other flavonoids to be an exciting treatment for prostate cancer patients, specific to inhibiton of fatty acids synthase activity /angiogenesis. However, can we get enough of the flavonoids in the olive leaf product to mount a successful campaign? I believe, with synergy, we will need at least 1gram of apigenin alone.
   A. It is difficult to know at this time with hardly any research done with apigenin and prostate cancer. Perhaps many types of flavonoids would help beside apigenin. Please see the prostate cancer page for updates.

Q. There is a great deal of very promising information about the potential value of apigenin at doses of about 150 mg/day in animal models of prostate cancer, and there are no apparent toxicities. However, I cannot find a source for apigenin in anything but trivial quantities. Do you know of such a source?
   A. I am not aware of any particular supplement companies that make an apigenin supplement product by itself.